By Muhammad OsamaReviewed by Lexie CornerJun 6 2025A recent study published in Scientific Reports looked at how different cleaning methods affect the physical and visual properties of 3D-printed orthodontic aligners.
The researchers tested brushing with and without toothpaste, as well as soaking in an alkaline cleaning solution, to help develop clear recommendations for aligner care. Understanding how these methods affect durability, surface texture, and color is important as clear aligners become more common in orthodontic treatment.
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Advances in Orthodontic Aligners
Clear aligners have revolutionized orthodontic treatment by offering a more comfortable and discreet alternative to traditional braces. Most aligners are made from thermoformed plastics like PETG, which are flexible and transparent.
However, they can wear down, develop surface roughness, and lose clarity over time. These changes can increase the risk of bacterial buildup and dental problems such as cavities and gum disease.
3D-printed aligners are made differently. They use polyurethane-based resins cured layer by layer with light. This method allows for better customization, but the materials may have more surface irregularities and pores. These features make them more likely to wear out or change shape when cleaned using standard methods.
Exploring Cleaning Effects on 3D-Printed Aligners
The study tested three cleaning methods on 3D-printed polyurethane aligners: soaking in Corega cleaning tablets, brushing with water, and brushing with toothpaste. A total of 84 rectangular samples were made using Clear A resin and a SprintRay Pro 95 3D printer. Samples followed international standards for mechanical testing.
After printing, the samples went through several post-processing steps: rinsing with ethanol, UV curing in glycerin, ultrasonic cleaning, and warming in water to simulate real-use conditions. The cleaning routines were done daily for 14 days to reflect normal patient use.
Researchers used atomic force microscopy and profilometry to measure surface roughness. They tested hardness using the Ball Indentation Method (ISO 2039-1). Color changes were measured using the CIEDE2000 (ΔE₀₀) formula and a VITA Easyshade colorimeter. They also tracked water absorption by weighing samples soaked in saline or Corega solution over time. Statistical methods like repeated measures ANOVA, Wilcoxon signed-rank tests, and Kruskal-Wallis tests were used to analyze the data.
Key Findings and Material Behavior Under Cleaning Protocols
Brushing, with or without toothpaste, significantly increased the surface roughness of 3D aligners, with the Toothbrush + Toothpaste group showing the highest increase. Soaking in Corega slightly reduced roughness, making it the gentlest option.
Brushed samples also became harder, likely due to the compaction of the surface or removal of softer, worn layers. In contrast, samples cleaned with Corega got slightly softer, possibly due to the loss of plasticizers or early-stage material breakdown. While these changes weren’t statistically significant, they suggest a balance between durability and flexibility.
There were no major color differences among the groups based on ΔE₀₀ values. However, all cleaning methods slightly changed color tones—Corega and brushing both shifted red-green values, while brushing also affected yellow-blue values. Over time, these changes might affect the aligners’ appearance.
Samples stored in saline steadily absorbed water and peaked at about 8.47 % by day 11. This reflects the natural water-attracting nature of polyurethane. In contrast, samples in Corega solution absorbed water at first but then lost some material, likely due to chemical breakdown. Water absorption and expansion could affect how well aligners fit and how force is applied during treatment.
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Applications for Orthodontic Practice and Material Development
This research has significant implications for clinical orthodontics and advancements in aligner materials. The increase in surface roughness from mechanical cleaning may promote bacterial growth and biofilm formation, compromising hygiene and aligner appearance.
Conversely, chemical cleaners like Corega tablets effectively remove plaque with minimal surface abrasion but may lead to polymer degradation over time. Given the tendency of 3D-printed aligners to absorb water and undergo dimensional changes, these factors should be considered when advising patients on cleaning practices and replacement schedules.
These findings highlight the need for material-specific cleaning guidelines that balance hygiene with aligner durability. Future work should focus on further exploring hybrid cleaning protocols that combine mechanical and chemical methods to improve cleaning efficacy while minimizing surface damage.
Long-term clinical studies are also needed to see how these cleaning routines perform in real-life settings. New materials or coatings that resist water uptake could also help make aligners last longer.
In short, this research supports better, more personalized strategies for cleaning and caring for 3D-printed orthodontic aligners, helping improve both performance and hygiene.
Journal Reference
Šimunović, L., et al. (2025). Impact of various cleaning protocols on the physical and aesthetic properties of 3D-printed orthodontic aligners. Sci Rep. DOI: 10.1038/s41598-025-04096-z, https://www.nature.com/articles/s41598-025-04096-z
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